Flowering stem erect, slender, straight, 15–55 cm long, 1–3.5 mm diam., green to purplish. Leaf linear to linear-lanceolate, attenuate, 10–28 cm long, 4–10 mm wide, fleshy, canaliculate, ribbed abaxially, sheathing at base, dark green with a purplish base. Inflorescence 1–8-flowered. Sterile bracts usually 2, rarely 1 or 3. Flowers pale blue to dark blue, sometimes pink; perianth segments ovate to lanceolate, 6–13 mm long. Column cylindric to quadrangular, 3–5 mm long, pinkish or pale blue; mid-lobe barely hooding, 0.5–1 mm long, c. 1 mm wide, yellow with a black subapical collar, apex with a 1–few rows of rounded calli; auxiliary lobes 0.6–1.5 mm long, converging, more or less rectangular, fleshy, porrect or obliquely erect, apex entire or shallowly toothed, yellow; lateral lobes 1–2 mm long, oblong, porrect or obliquely erect, apical margins with a toothbrush-like arrangement of white hairs. Anther inserted near middle of column, with a slender incurved beak protruding below the lateral lobes. Flowers Oct.–Dec.
GipP, EGL, HSF, HNF. Also NSW, Tas. Grows in coastal and near-coastal heathland and heathy woodland in low-lying moist areas or drier sites on sandy, clay or peaty loams.
Thelymitra longiloba has been confused with T. media, but can be distinguished by its generally earlier flowering season, less robust nature, smaller flowers and longer, narrower auxiliary lobes on the column.
Flowers open freely in warm to hot weather and are self-pollinating.
